1. Field of the Invention
The present invention relates to a photoelectric converting apparatus and, more particularly, to a photoelectric converting apparatus, in particular, a long line sensor which is used to read an image in the facsimile apparatus, image reader, digital copying apparatus, electronic blackboard, or the like.
2. Related Background Art
In recent years, the long line sensor having an equal magnification optical system has been developed in order to reduce the size of and improve the performance of the facsimile apparatus, image reader, or the like. Hitherto, this kind of line sensor is constituted in such a manner that signal processing ICs (integrated circuits) each of which is constituted by switch elements and the like are connected to each of the sensor elements arranged in a line array form. However, in the case of complying with the G&gt;&gt; standard of the facsimile, 1728 sensor elements are necessary for the A4 size and a number of signal processing ICs are also needed. Therefore, the number of installation steps to attach the signal processing ICs also increases and the long line sensor which can satisfy both of the manufacturing cost and the reliability is not obtained yet. On the other hand, the constitution based on the matrix connection has conventionally been used in order to reduce the number of signal processing ICs and the number of installation steps.
However, such a conventional matrix constitution has the following problems.
(1) Since very low level sensor currents are read out through the matrix connection, if the stray capacitances which are formed in the insulation crossing portions between the electrodes on the sensor side and the (common) electrodes on the matrix output side are not sufficiently reduced, a signal crosstalk will be caused between the outputs of the respective sensors. This results in severe limitations in selection of an insulating material between layers and in dimensions and design of the matrix.
On the other hand, it is desirable to form the sensor unit and the matrix unit on the same substrate in order to reduce the costs and improve the reliability and the like. However, in general, the photoconductive material is formed by a low temperature process. On the contrary, a high temperature is required to form the insulating film between layers having good characteristics. Thus, it is difficult to simultaneously mixedly form the sensor unit and the matrix unit by both of the low temperature process and the high temperature process. Further, even if the matrix unit and the sensor unit are separately formed by the foregoing processes in accordance with the order of the high temperature process and the low temperature process, its manufacturing cost will increase.
(2) If a leak resistance is caused by a pin hole or the like even at one of the insulation crossing portions of the matrix unit, the signal output becomes defective and the sensors of all blocks are adversely influenced. This causes the matrix yield to remarkably deteriorate.
(3) Since the matrix common electrodes a.sub.1 to a.sub.M are arranged in the longitudinal direction, the length of line sensor in the case of the width of, e.g., A4 size is set to 210 mm. Therefore, it is necessary to sufficiently reduce the leak resistance and capacitance between the respective output lines. The values of the leak resistance and capacitance between lines are concerned with the distance between the adjacent wiring patterns. The size of matrix unit cannot be so decreased.
It is an object of the present invention to eliminate the foregoing conventional drawbacks and to provide a photoelectric converting apparatus of a good yield and a low cost in which the small matrix unit can be formed on the same substrate as that of the sensor unit by the low temperature process which is almost equal to the temperature to form the sensor unit.
On the other hand, in such a conventional photoelectric converting apparatus, the matrix unit is constituted on the output line side of the transferring switch elements in order to sequentially read out the signals from one side. Thus, there is such a drawback that the signal lines as many as only the output lines of the switch elements which are turned on by a single gate line cross and a leak current flows due to the capacitances between the lines, so that very large crosstalk is caused.
It is an object of the present invention to eliminate the foregoing drawbacks and to provide a photoelectric converting apparatus in which the crossing portions of the signal lines are constituted in the portions which do not exert any influence to the transfer charges.